I am making changes to an image in Lightroom using a mask. I am changing the background to B&W. However when I export it the changes are lost. See attached screengrabs. Thanks for your help
This is a common misunderstanding. You have not changed the background to B&W, you have activated a mask overlay that shows the non-masked area in B&W. A mask overlay is not an edit, it's a way of showing you which parts of the image will be edited in the mask and which parts will not be affected. In order to make an edit that turns the background B&W do the following: Select the mask and click the 'Inverse' checkbox. Now you are editing the background. Now set the Saturation slider all the way to -100 to make the masked area lose all its color.